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SARS-CoV-2 symptoms are non-specific and can range from asymptomatic presentation to severe pneumonia. Asymptomatic subjects carrying SARS-CoV-2 often remain undiagnosed and it is still debated whether they develop immunoglobulins (Ig) and how long they persist. The aim of this study was to investigate the development and persistence of antibodies against SARS-CoV-2 in asymptomatic subjects infected by the virus. This follow-up study was performed on the 31 asymptomatic subjects who presented a positive nasal swab or serology against SARS-CoV-2 (Ig against Spike-RBD) in the first part of the UNICORN study (March 2020) aimed at attesting previous or current contacts with the virus in the personnel of the University of Milan. Eight weeks after the first Ig measure, these subjects were invited to donate a second blood sample for testing serum antibodies (IgM, IgG and total antibodies) and to fill-in a structured questionnaire. About 80% of asymptomatic subjects did not present circulating immunoglobulins against SARS-CoV-2 after 8 weeks from a positive nasal swab against the virus. Moreover, in more than 40% of these subjects, no Ig against SARS-CoV-2 were detected at any time. Finally, about two third of subjects with immunoglobulins at baseline did not present IgG against SARS-CoV-2 after 8 weeks. The majority of subjects who developed an asymptomatic SARS-CoV-2 infection do not present antibodies against the RBD-spike protein after 8 weeks of follow-up. These data should be taken into account for the interpretation of the serological evidences on SARS-CoV-2 that are emerging nowadays.

Decades after smallpox was eradicated and vaccination discontinued, the level of residual immunity in today's population is largely unknown. This study describes an epidemiological assessment in Italians of antibodies against the intracellular mature virus (IMV) and extracellular envelope virus (EEV) forms of Vaccinia virus. Serum samples (n=642) were taken in 1993 and 2003 from people between 11 and 102 years old. Most citizens >27 years old were positive for antibodies to IMV and EEV. These antibodies were long-lasting and similar titres were present in citizens between 30 and 100 years old. Serum samples from 1993 and 2003 displayed very similar EEV-and IMV-specific antibody titres. By using these data and demographic considerations, it was predicted that, in 2003, 46 % of the Italian population were positive for both IMV and EEV, 42 % were negative for both and 12 % were positive for one antigen.Variola virus, the causative agent of smallpox, was eradicated in 1977 after widespread vaccination with Vaccinia virus (VACV) (Fenner et al., 1988). In Italy and many other European countries, smallpox vaccination used predominantly VACV strain Lister/Elstree. Vaccination was compulsory in Italy until 1976(Tagarelli et al., 2004 although, after 1974, public-health services were less stringent in their vaccination policy. Mass smallpox vaccination was abandoned in most European countries in the early 1970s and production of the vaccine was discontinued in the early 1980s.Understanding of the immune responses induced after vaccination with VACV is incomplete and concern about the deliberate release of Variola virus (Smith & McFadden, 2002) has prompted investigation of how much immunity remains in populations today. It was generally accepted that vaccination would protect most vaccinees for 5-10 years (Fenner et al., 1988), although the World Health Organization (WHO) recommended revaccination every 3 years for those in areas where smallpox was endemic. Recent studies have shown that humoral (Crotty et al., 2003;Frey et al., 2003;Gallwitz et al., 2003;Hammarlund et al., 2003;Hatakeyama et al., 2005;Viner & Isaacs, 2005) and cellular (Hammarlund et al., 2003;Amara et al., 2004;Combadiere et al., 2004;Kennedy et al., 2004) forms of immunity are long-lived after VACV immunization, but it is unknown whether this remaining immunity will protect against smallpox. Although analysis of historical data suggests that protection after vaccination might last for several decades (Hanna & Baxby, 2002;Eichner, 2003a), the last smallpox fatality, in Birmingham, UK, in 1978, occurred despite the patient having been vaccinated twice previously, once as a child and once 12 years before contracting the disease (Shooter, 1980). VACV produces two morphologically and antigenically distinct infectious forms of virus, called intracellular mature virus (IMV) and extracellular envelope virus (EEV) . Most infectious virus particles remain in the cell as IMV until cell lysis; this form is very stable and so is likely to be responsible for host-to...

In the 20th century, three influenza pandemics killed approximately 100 million people. The traditional method of influenza vaccine manufacturing is based on using chicken eggs. However, the necessity of the availability of millions of fertile eggs in the event of a pandemic has led research to focus on the development of cell culture-derived vaccines, which offer shorter lead-in times and greater flexibility of production. So far, the cell substrates being evaluated and in use include Vero, Madin-Darby canine kidney, PER.C6 and insect cells. However, Vero cells are the most widely accepted among others. This review introduces briefly the concepts of advanced cell culture-derived influenza vaccine production and highlights the advantages of these vaccines in terms of efficiency, speed and immunogenicity based on the clinical data obtained from different studies.

Influenza D virus is a novel influenza virus, which was first isolated from an ailing swine in 2011 and later detected in cattle, suggesting that these animals may be a primary natural reservoir. To date, few studies have been performed on human samples and there is no conclusive evidence on the ability of the virus to infect humans. The aim of this serological study was to assess the prevalence of antibodies against influenza D virus in human serum samples collected in Italy from 2005 to 2017. Serum samples were analysed by haemagglutination inhibition and virus neutralization assays. The results showed that the prevalence of antibodies against the virus increased in the human population in Italy from 2005 to 2017, with a trend characterized by a sharp increase in some years, followed by a decline in subsequent years. The virus showed the ability to infect and elicit an immune response in humans. However, prevalence peaks in humans appear to follow epidemics in animals and not to persist in the human population.